My go-to explanation of acceptable political opinions is usually the Overton Window, but this week I came across Hallin’s spheres:
Hallin’s spheres is a theory of media objectivity posited by journalism historian Daniel C. Hallin in his book The Uncensored War to explain the coverage of the Vietnam war. Hallin divides the world of political discourse into three concentric spheres: consensus, legitimate controversy, and deviance. In the sphere of consensus, journalists assume everyone agrees. The sphere of legitimate controversy includes the standard political debates, and journalists are expected to remain neutral. The sphere of deviance falls outside the bounds of legitimate debate, and journalists can ignore it. These boundaries shift, as public opinion shifts.Wikipedia
I think the interesting thing right now for either theory is that most people have their news filtered by social networks. As a result, it’s not (just) journalists doing the filtering, but people in affinity groups.